Advertising was once a huge but varied industry. Newspapers, TV, radio, magazines, billboards, and plenty of other media competed for their own piece of the pie.

The digital world could not be more different. Online ads are dominated by Google and Facebook—and they’re only getting bigger. Google and Facebook are projected to take up 63.1 percent of U.S. digital ad spending in 2017—even more than had been initially expected, according to eMarketer.